1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to a transflective LCD device and a method of fabricating the same.
2. Discussion of the Related Art
Generally, a transflective liquid crystal display (LCD) device functions both as a transmissive LCD device and a reflective LCD device. Transflective LCD devices are more versatile because they can use both a backlight and ambient light as light sources. Moreover, transflective LCD devices have low power consumption.
FIG. 1 is an exploded perspective view of an LCD device according to the related art. As shown in FIG. 1, an LCD device 10 has an upper substrate 30 having a black matrix 34. A color filter layer 32 of the LCD device 10 includes red, green, and blue sub-color filters 32a, 32b, and 32c, respectively. The LCD device 10 includes a common electrode 36 on the color filter layer 32, and a lower substrate 20 having a switching element, such as a thin film transistor (TFT) T, and a transparent electrode 24 connected to the TFT T. A liquid crystal layer 45 is interposed between the upper and lower substrates 30 and 20. The lower substrate 20 is referred to as an array substrate because an array of lines, including gate lines 21 and data lines 22, is formed thereon. The gate lines 21 and the data lines 22 cross each other to form a matrix. The TFT T is connected to one of the gate lines 21 and one of the data lines 22. The TFT T is formed near a crossing of the gate lines 21 and the data lines 22. The transparent electrode 24 is formed of a transparent conductive material, such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO), in the pixel region P. A reflective electrode 26 includes a reflective metallic material, such as aluminum (Al), and has an opening portion exposing a portion of the transparent electrode 24. The opening portion defines a transmissive region A1 and a region of the reflective layer 26 excluding the opening portion defines a reflective region A2. The transmissive region A1 and the reflective region A2 constitute a pixel region P. The upper substrate 30 is referred to as a color filter substrate because the color filter layer 32 is formed thereon. As explained above, the transmissive region A1 and the reflective region A2 can be manufactured having various shapes.
FIG. 2 is a schematic plan view of an array substrate for a transflective LCD device according to the related art. As shown in FIG. 2, a first substrate 50 includes a pixel region P that includes a transmissive region A1 and a reflective region A2. A gate line 52 is formed on the first substrate 50 along a first direction, and a data line 66 crosses the gate line 52 along a second direction. A reflective layer 74 is disposed in the reflective region A2 and has an open portion OP corresponding to the transmissive region A1. A pixel electrode 78 of a transparent electrode is exposed by the open portion OP.
A thin film transistor T is formed near a crossing of the gate line 52 and the data line 66 and includes a gate electrode 54, a semiconductor layer SL, a source electrode 62 and a drain electrode 64. A common line 56 is formed along the first direction and is spaced apart from the gate line 52. A first capacitor electrode 60 is extended from the common line 56 and a second capacitor electrode 68 is extended from the drain electrode 64, wherein the first capacitor electrode 60, the second capacitor electrode 68, and an insulating layer (not shown) therebetween constitute a storage capacitor Cst.
The transmissive regions A1 and the reflective regions A2 of the respective pixel regions P are disposed in parallel to each other. Further, the reflective layer 74 is patterned in the pixel region P and is spaced apart from an adjacent reflective layer 74. Accordingly, the data lines 66 are exposed by the space between the reflective layers 74. Hence, the exposed regions of the data line 66 need to be covered using a light interception means such as a black matrix.
FIG. 3 is a schematic cross sectional view taken along a line III-III of FIG. 2 according to the related art. As shown in FIG. 3, a first substrate 50 includes a pixel region P, a first common line pattern 58a, and a second common line pattern 58b, the first and second common line patterns 58a and 58b being extended from the common electrode 56 (of FIG. 2). A data line 66 is formed over the first and second common line patterns 58a and 58b in a non-pixel region (not shown) that is disposed in a periphery of the pixel region P. An organic layer 70 is formed over the data line 66 to prevent an electric interference, and a reflective layer 74 is formed over the organic layer 70.
The reflective layer 74 covers a side portion SP of the organic layer 70 having a step difference including a portion of the pixel region P. A transparent pixel electrode 78 is independently formed in the pixel region P. Substantively, because the pixel electrode 78 is formed in the transmissive region A1 as well as the reflective region A2, the reflective layer 74 does not act as an electrode.
An aperture region of the transflective LCD device depends on a size of the transmissive region A1. However, the transflective LCD device according to the related art has space limitations preventing expansion of the aperture region. Because the transmissive regions A1 and the reflective regions A2 of the pixel regions P are aligned side-by-side, the potential for signal interference between the pixel electrode 78 of one pixel region and the data line 66 of an adjacent pixel region, a workable space for each pixel region is predetermined based on the dimensions of the electrical components of the LCD device.
In the related art, the mentioned organic layer 70 is formed to minimize the electric interference between the pixel electrode 78 and the data line 66. The inclusion of the organic layer 70 creates a step difference in the side portion SP of the organic layer 70. This step profile allows light to leak out in portions of the pixel electrode 78 covered by the side portions SP of the organic layer 70 because the portions of the pixel electrode 78 corresponding to the side portions SP of the organic layer 70 are misaligned. The main role of the organic layer 70 is to provide a gap between the reflective region A2 and the transmissive region A1, such as a cell gap ratio of 1 to 2 (1:2), in order to obtain a uniform optical effect. Accordingly, the step difference of the side portion SP of the organic layer 70 is necessarily present in a cell gap structure of the transflective LCD device of the related art.
In order to minimize the visual effect of the light leakage around the side portions SP, a black matrix 92 is formed on a second substrate 90. In the transflective LCD device of the related art, the black matrix 92 needs to have a width (W1) that includes widths of the side portions SP (W2) as well as a width of the data line 66 (W3). As a result, the transflective LCD device according to the related art has limited aperture ratio that cannot be readily increased due to the structural arrangement between the transmissive region A1 and the reflective region A2 having the cell gap difference between the transmissive region A1 and the reflective region A2. Although not explained above, the second substrate 90 further includes a color filter layer on the black matrix 92 and a common electrode (not shown) on the color filter layer, and a liquid crystal layer is interposed between the first and second substrates 50 and 90.